We present the results of an 18 mo survey of the seasonal activity
and species composition of dung beetles (Scarabaeidae: Scarabaeinae and
Aphodiinae and Geotrupidae: Geotrupes) from a cattle pasture on
Crowley's Ridge, Arkansas, and of 17 additional surveys, at various
localities and habitats across Arkansas. Collections at the cattle
pasture comprised 236,880 beetles, representing 22 species. Labarrus
pseudolividus Balthasar comprised 97.7% of the total trap catch, with
the majority being collected in Jun., Jul. and Aug. 2007 which involved
two separate mass occurrences during that time. From all surveys, we
documented 22 state records, of which Colobopterus erraticus (Linnaeus)
and Onthophagus taurus (Schreber) represented subtle range extensions to
their known distributions, while the remaining 20 species were projected
to occur in Arkansas. A checklist, distributional record and
bibliography of the 64 species of dung beetles that are now known to
occur in Arkansas are presented.

By fragmenting and burying excrement, dung beetles (Scarabaeidae:
Scarabaeinae and Aphodiinae and Geotrupidae) are an important ecological
component in both natural and artificial ecosystems (Bornemissza, 1960;
Fincher, 1981; Nichols et al., 2008). Therefore, there is general
interest among ecologists and cattle producers in research that aims to
conserve and manage these beneficial beetles. Towards this end, to
survey dung beetles and catalog their phenologies within a geographic
region are the first necessary efforts. Surveys of Scarabaeoidea, which
include dung beetles, have been conducted in a number of states (see
Kriska and Young, 2002 for review; Riley and Wolfe, 2003). For example,
in Texas, the diversity of dung beetles collected in each of seven
regions ranged from 44-91 species (Riley and Wolfe, 2003). Limited niche
specific surveying has been done in Arkansas (e.g., Ozark pocket gopher,
Geomys bursarius ozarkensis Elrod, Zimmerman, Sudman & Heidt,
burrows, Kovarik et al., 2008). For the six physiographic regions in
Arkansas, only 43 species of dung beetles have been documented to date.
Thus, there seemed to be potential to increase the known dung beetle
fauna of Arkansas through further surveying efforts of both natural
(e.g., forests) and artificial (e.g., cattle pastures) habitats.

We surveyed dung beetles at various localities and habitats across
Arkansas to document the dung beetle species and their distributions
within the state. The primary study presents the results of an 18 mo
survey of dung beetles on Crowley's Ridge. This study is important
because it was the first effort to identify dung beetles on
Crowley's Ridge in Arkansas, while also being the first survey to
document the phenologies and species composition of an assemblage of
pasture-inhabiting dung beetles in all of Arkansas.

MATERIALS AND METHODS

Primary locality description.--The primary study was conducted at
the Arkansas State University (ASU) Farm Complex inJonesboro, Craighead
County, Arkansas. The loessal soil type at the ASU Farm Complex is
classified as Loring-Grenada-Henry and is characterized as deep, well-
to poorly-drained and slowly permeable (Crow, 1974). The ASU Farm
Complex is located on Crowley's Ridge, which is an area of rolling
hills that rises abruptly 60-90 m from the flat delta land surrounding
it. The Ridge ranges from 1.6 to 16 km wide and runs from southern
Missouri to Helena, Arkansas (240 kin-long), encompassing portions of
Clay, Greene, Craighead, Poinsett, Cross, St. Francis and Lee Counties.
Crowley's Ridge is an erosional remnant of a higher plain from
which the present alluvial plain was carved during the Pleistocene
interglacial periods when the Mississippi River meandered to the west of
the ridge and the Ohio River to the east (Crow, 1974). The vegetation
that occurs on Crowley's Ridge is more closely related to the flora
(e.g., tulip tree-oak forests) of Tennessee than to the oak hickory
forests of the Ozarks, indicating that the biota of Crowley's Ridge
had a more recent connection with the Tennessee biota than with the
biota of the Ozark/ Ouachita area in Arkansas (Robison and Allen, 1995).
Additionally, since Crowley's Ridge has been traditionally used for
livestock production and is surrounded by delta that is typically used
for crop production (B. Humphrey, pers. comm.), it is a unique area to
study dung beetle diversity.

The study site was comprised of two adjacent pastures that were 3.2
and 4.0 ha of open pasture, respectively, each with 0.81 ha of mature
hardwood timber. A herd of Angus crossbred cattle, Bos taurus Linnaeus,
were rotated between the two pastures, which consisted of tall fescue,
Festuca arundinacea Schreber, and Bermuda grass, Cynodon dactylon
(Linnaeus). Climatological data were acquired through the Jonesboro
Airport weather station that was located 1 km from the study site.

We monitored the seasonal activity of adult dung beetles from 27
Mar. 2007 to 28 Sept. 2008. We evenly spaced ten baited pit-fall traps
(-23 m apart) in the open pasture along the fence (253 m) that separated
the two pastures. Traps 1 and 10 were ~23 m from the edge of the pasture
and the wooded timber, respectively. Traps consisted of two buckets
(19.0 cmw X 23.5 cm h), one placed inside the other, with a wire mesh
(2.5 cm X 2.5 cm) over the mouth of the trap to support the dung baits.
Baits were made of cattle dung (~75 g) wrapped in cheesecloth. The
cattle dung was collected fresh (<3 h) and frozen until use (-20 C).
We buried the traps in the ground with the lip of the trap level with
the soil surface. Then, we added a solution of water (~1 liter), laundry
detergent (~50 ml), and table salt (~60 g) to each trap. Vegetation
within 0.5 m of the traps was trimmed to less than 5 cm to enhance
dispersal of bait odors. Beetles were removed from traps and baits were
replaced on a weekly basis throughout most of the study except during
winter months (Nov. through early Feb.) when beetles were collected
bi-weekly. In total, we collected beetles from 69 trapping periods
throughout the 18 mo study. On five occasions a trap was either filled
with mud or tipped over and was removed from analysis. Beetles were
stored in 70% ethanol until they were sorted, counted and identified.
When traps consisted of >6000 beetles, bulk samples of beetles were
oven-dried for 5 d at 55 C and then weighed. The number of beetles in
the bulk sample was then estimated using the average number of beetles
per gram calculated from five subsamples of 0.2 g or 0.5 g.

Phenologies of beetles were examined by pooling the total number of
individuals collected from all traps during a baiting period. We
separated months in which beetles had been collected from both years to
compare annual patterns of species composition.

Additional localities.--To supplement the aforementioned study with
an updated state list, dung beeries were also collected at 17 additional
localities in Arkansas. Our efforts to collect beetles occurred from
1995-2009 and varied among each locality in the frequency and method of
collection. In general, beetles were collected from flight intercept
traps, ultraviolet and black lights traps and/or at various types of
patchy resources (fruit, carrion, excrement, mushrooms) that were used
as baits for pitfall traps or from which beetles were collected in situ.
The collection labels are reported in the following format: Month
(year), collection method, County (specific locality description),
number of specimens collected; additional locality.

Taxonomic identification.--We identified beetles to species level
by using taxonomic keys (Robinson, 1948a; Howden, 1955; Howden and
Cartwright, 1963; Cartwright, 1974; Edmonds, 1994; Genier, 2000;
Ratcliffe et al., 2002; Gordon and Skelley, 2007) with reference to
specimens in the Arkansas State University collection, Texas A&M
University collection, and the Carnegie Museum of Natural History and
personal communication with Dr. Paul Skelley (Florida Department of
Agriculture and Consumer Services--Division of Plant Industry) and Ed
Riley (Texas A&M University, Department of Entomology).

RESULTS

Primary locality.--We collected a total of 236,880 beetles
representing 22 species from the cattle pasture survey on Crowley's
Ridge (Table 1). Labarrus pseudolividus Balthasar represented 97.7% of
the composition. The majority of L. pseudolividus (211,485 individuals)
were collected in the months of Jun., Jul. and Aug. in 2007 (Fig. 1A).
The presence of L. pseudolividus occurred from Apr. through Nov. with
two periods of high abundance. Each peak lasted for roughly 1 mo, with
the first peak starting in mid-Jun, in both years, while the second peak
was variable and started in late Jul. in 2007 and late Aug. in 2008.

The seasonal activity for all species at the ASU Farm Complex is
reported for those represented by >2 individuals (Figs. 1-5), and
those represented by <2 individuals (Table 1). In general, the
majority of beetles were collected during the summer when the ambient
temperature was greatest and precipitation was lowest (Fig. 6). The
average daily maximum temperature for each year (Apr.-Sept.) was 29.9 C
in 2007 and 27.3 C in 2008. Total precipitation for each year
(Apr.-Sept.) was 33.5 cm in 2007 and 48.3 cm in 2008.

Additional localities.--A total of 30 species of dung beetles were
collected from 17 additional localities across Arkansas and are
presented as follows:

The beetle comprising the majority of the samples from the cattle
pasture survey, Labarrus pseudolividus, is a small (3.5-5.8 mm),
'dweller' beetle that oviposits and develops
'freely' in the resource (Cambefort and Hanski, 1991).
Possibly native to North America, this species is widely distributed
(southern United States, south to Chile and Argentina), and commonly
collected in southern North America (Gordon and Skelley, 2007). Gordon
and Skelley (2007) found that most nearctic specimens previously
identified as Labarrus lividus Olivier sensu lato Aphodius lividus, were
L. pseudolividus. Therefore, citations of L. lividus will be included;
however, in all cases it is not known if the type specimens in these
studies agree with the general misidentification of this species.

Using developmental data of Labarrus lividus, which completes
development from egg to adult in 25-45 d, the bimodal activity of L.
pseudolividus evidenced by the large collection in Jun. and Aug. (Fig.
1), was interpreted as the emergence of the first filial ([F.sub.1]),
over-wintering generation in Jun. and the emergence of the second filial
generation ([F.sub.2]) in Aug. (Lindquist, 1935). Large collections of
dung beetles using baited pitfall traps are not entirely uncommon
(Fincher et al., 1986; Hanski and Cambefort, 1991; Floate and Gill,
1998; Bertone et al., 2005). Yet the abundance and dominance of L.
pseudolividus was somewhat unique with respect to similar surveys. It
seems these abundances were reflective of an event called a mass
occurrence that, seemingly, happened in both generations in that year.
Such events have been reported for beetle species whose densities reach
in the hundreds or thousands of individuals per dung pat (Table 2),
while our results described one of these events at a substantially
larger scale (7.2 ha study site). Seamans (1934) reported Aphodius
distinctus Muller (now Chilothorax distinctus) to mass occur annually in
the "countless thousands" in the spring and autumn. The
results of this study, conducted over 2 y, indicated greater
between-year variation than the descriptions presented by Seamans (1934)
and support the observation by Finn and Gittings (2003) that these
events occur at a low frequency. Interestingly, mass occurrences have
involved species whose larvae exhibit some degree of either obligate or
facultative saprophagy (Hanski, 1991; Finn and Gittings, 2003). This
holds true for the larval feeding habits of L. pseudolividus (Gordon and
Skelley, 2007), and is potentially an important clue for understanding
the large abundance collected in 2007 (Hanski, 1991; Finn and Gittings,
2003). For this to be the case, the influx in the developmental resource
would have come about in the fall of 2006 (when the adult [F.sub.2]
generation of 2006 were ovipositing) and also in Jun. of 2007 when the
[F.sub.1] generation were ovipositing. At this point, such a scenario
seemingly raises more questions than answers, and highlights the need
for additional research. To address the developmental habitat hypothesis
for mass occurences and to better understand adult abundances in
general, future research should sample for larvae in a variety of
developmental habitats i.e., dung pats, soil (K. D. Floate, pers.
comm.), near the feeding rings where hay accumulates and leaf litter.

Onthophagus gazella (Fabricius) is an exotic species of dung beetle
that was released in northwest Arkansas at two sites in the late 1970s,
but failed to establish (Lancaster and Hunter, 1978). In 1983, the
species was reported from southwest Arkansas and was thought to have
dispersed from Louisiana and/or Texas (Hunter and Fincher, 1985).
Assuming that this species is colonizing new localities in a northern
direction, it is likely the range extension of O. gazella to
northeastern Arkansas did not occur recently since this species was
collected in southeastern Missouri in 1997 (MacRae and Penn, 2001).
Onthophagus gazella completes development in ~30 d (Blume and Aga,
1978), and could possibly complete 5-6 generations each year being
active from Jun. through Nov. in our study. In both years a single peak
in collections of O. gazella (encompassing multiple collection dates)
was observed (Fig. 2A) suggesting a univoltine natural history; however,
this has not been experimentally verified.

We collected two exotic species, Onthophagus taurus and
Colobopterus erraticus, that are new state records and represented
subtle range extensions from their known distributions. Onthophagus
taurus is an exotic species that was accidentally introduced to Florida
in 1971 (Fincher and Woodruff, 1975). Since its initial detection, O.
taurus had been released in northwest Arkansas where its establishment
is uncertain (Lancaster and Hunter, 1978). It has been collected in
three neighboring states: central Mississippi, eastern Tennessee and
southern Missouri (Lago, 1979; Hoebeke and Beucke, 1997; MacRae and
Penn, 2001). Aside from releases in California and Texas, O. taurus
appears to be restricted to the eastern United States (Hoebeke and
Beucke, 1997). Because O. taurus has not been reported from Iowa,
Illinois or Indiana, the populations in southern Missouri possibly
originated from Arkansas or Tennessee as a northward expansion.
Therefore, three scenarios could have lead to the population of O.
taurus on Crowleys Ridge: (1) the Franklin County population in
northwestern Arkansas established in 1978 and spread east, (2) the
Mississippi/ Tennessee populations expanded north and west, (3) both
Franklin County and Mississippi/Tennessee populations merged at an
unknown location within the last 29 y, suggesting the Crowley's
Ridge population is a mix of both of these populations. In Jun. 2009, O.
taurus was collected from the Ozark plateau in southern Marion County
and northern Searcy County, Arkansas. This location is approximately
half way between Franklin County and Crowley's Ridge. Trapping for
O. taurus at the release site in Franklin County would address these
hypotheses, especially if no specimens are collected. At our study site,
we observed 5-6 peaks of O. taurus (Fig. 1B) that we roughly correlated
with 5-6 completed generations given its eight month seasonal activity
and developmental time of 4-5 weeks, depending on temperature (Wardhaugh
et al., 2001).

Colobopterus erraticus is a species native to Europe that was
accidentally introduced to the United States (Gordon and Skelley, 2007).
The distribution of this species is Nova Scotia, south to Georgia, west
and north to Missouri, Montana and British Columbia (Hunter et al.,
1987; Gordon and Skelley, 2007). States between Georgia and Arkansas
(Alabama, Mississippi and Tennessee) have no records of C. erraticus and
tentatively suggest the Crowley's Ridge population originated in
Missouri. Collections of this species occurred from Apr. through mid
Jun. (Fig. 3A), and with a developmental time of 6-7 wk (Rojewski,
1983), it is likely C. erraticus is univoltine.

The present study adds 22 dung beetle species to the known insect
fauna of Arkansas, 20 of which were projected to occur but not
documented (Table 3). This study increased the known dung beetle fauna
in Arkansas by 66%, highlighting the importance of additional statewide
dung beetle survey, and the investigation of museum collections to
produce new records and/or validate suspected occurrences. We also
documented a significant collection of Labarrus pseudolividus over a
period of about 3 mo using baited pitfall traps, which apparently
involved two separate mass occurrences during that time. These events
caused the dung pats appearance to be generally flattened, with the
periphery having a saw-dust consistency and likely had positive effects
on the degradation. Understanding the nature of mass occurrences so that
we are able to more actively predict and control these events has
convincing potential for increasing the efficiency of cattle and pasture
management. Future research on the dung beetles in Arkansas has
potential for elucidating a poorly understand phenomenon called a mass
occurrence and for the documentation of additional species and their
distributions within the state.

Acknowledgments.--We thank Paul Skelley (Florida Department of
Agriculture and Consumer Services--Division of Plant Industry) and Ed
Riley (Texas A&M University) for confirmation of species
identifications, Kevin Floate (Agriculture and Agri-Food Canada,
Alberta, Canada) and two anonymous reviewers for comments on an earlier
version of this manuscript and Mike Johnson (Arkansas State University)
for technical support at the research site. This project was partially
funded by the Arkansas Biosciences Institute and the Arkansas Game and
Fish Commission. Voucher specimens were placed in the Arkansas State
University Museum, Carnegie Museum of Natural History and the Florida
State Museum Collection of Arthropods.

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